Separator for lithium secondary battery, method of producing the same, and electrochemical device including the same

Patent metadata

Field	Value
Publication number	US-12113238-B2
Application number	US-202117463907-A
Country	US
Kind code	B2
Filing date	Sep 1, 2021
Priority date	Sep 10, 2020
Publication date	Oct 8, 2024
Grant date	Oct 8, 2024

Abstract

Provided is a separator for a lithium secondary battery including a porous substrate and a coating layer including a binder and inorganic particles formed on one surface or both surfaces of the porous substrate. The binder is a binder including: (a) a (meth)acrylamide-based monomer polymerization unit, (b) a (meth)acryl-based monomer polymerization unit containing a hydroxyl group, and (c) a polyfunctional (meth)acrylamide-based monomer polymerization unit. The separator according to the present invention provides a separator for a lithium secondary battery having improved adhesive strength between the inorganic particles and the separator, showing a decreased interfacial resistance characteristic, and showing an improved air permeability.

First claim

What is claimed is:

1. A separator for a lithium secondary battery comprising:
a porous substrate; and
a coating layer comprising a binder and inorganic particles formed on one surface or both surfaces of the porous substrate,
wherein the binder is a binder comprising: (a) 68 to 93 mol % of a (meth)acrylamide-based monomer polymerization unit, (b) 6 to 31 mol % of a (meth)acryl-based monomer polymerization unit containing a hydroxyl group, and (c) 0.005 to 0.041 mol % of a polyfunctional (meth)acrylamide-based monomer polymerization unit,
wherein (b) the (meth)acryl-based monomer polymerization unit containing a hydroxyl group is represented by the following Chemical Formula 2:

wherein
R 2 is hydrogen or a C1 to C6 alkyl group, and
L 1 is a linear or branched C1 to C6 alkylene group.

2. The separator for a lithium secondary battery of claim 1 , wherein (c) the polyfunctional (meth)acrylamide-based monomer polymerization unit is produced by polymerizing a polyfunctional monomer represented by the following Chemical Formula 3:

wherein
R 1 and R 2 are independently of each other hydrogen or a C1 to C6 alkyl group,
R is a linear or branched C1 to C10 hydrocarbon group, and
a is an integer of 2 to 6.

3. The separator for a lithium secondary battery of claim 1 , wherein the binder has a weight average molecular weight of 100,000 to 2,000,000 g/mol.

4. The separator for a lithium secondary battery of claim 1 , wherein the coating layer comprises 50 to 99.9 wt % of the inorganic particles and 0.1 to 50 wt % of the binder based on a total weight of the coating layer.

5. The separator for a lithium secondary battery of claim 1 , wherein the separator for a lithium secondary battery has a shrinkage rate both in a machine direction (MD) and a transverse direction (TD) of 5% or less after being allowed to stand at 150° C. for 60 minutes.

6. The separator for a lithium secondary battery of claim 5 , wherein the separator for a lithium secondary battery has a shrinkage rate both in the machine direction (MD) and the transverse direction (TD) of 3% or less after being allowed to stand at 150° for 60 minutes.

7. The separator for a lithium secondary battery of claim 1 , wherein the separator for a lithium secondary battery has a change amount of air permeability (ΔG) satisfying the following Equation 1:
Δ G=G 1− G 2≤70  [Equation 1]

wherein
G1 is a Gurley permeability of the separator comprising the coating layer,
G2 is a Gurley permeability of the porous substrate itself, and
the Gurley permeability is measured in accordance with ASTM D726 and has a unit of sec/100 cc.

8. The separator for a lithium secondary battery of claim 1 , wherein the coating layer has a thickness of 0.3 to 10 μm.

9. A lithium secondary battery comprising the separator for a lithium secondary battery of claim 1 .

10. A method of producing a separator for a lithium secondary battery, the method comprising:
(s1) preparing a slurry composition comprising a binder and inorganic particles; and
(s2) applying the slurry composition on one surface or both surfaces of a porous substrate to form a coating layer,
wherein the binder is a binder comprising: (a) 66 to 93 mol % of a (meth)acrylamide-based monomer polymerization unit, (b) 6 to 31 mol % of a (meth)acryl-based monomer polymerization unit containing a hydroxyl group, and (c) 0.005 to 0.041 mol % of a polyfunctional (meth)acrylamide-based monomer polymerization unit,
wherein (b) the (meth)acryl-based monomer polymerization unit containing a hydroxyl group is represented by the following Chemical Formula 2:

wherein
R 2 is hydrogen or a C1 to C6 alkyl group, and
L 1 is a linear or branched C1 to C6 alkylene group.

Assignees

• Sk Innovation Co Ltd
• Sk Ie Tech Co Ltd

Inventors

• Kwon Tae Wook
• Bae Heung Taek
• Lee Dong Yeon
• Kim Yun Bong

Classifications

• H01M10/052 Primary

  Li-accumulators · CPC title

• H01M50/42

  Acrylic resins · CPC title

• H01M50/449

  having a layered structure · CPC title

• H01M50/403 Primary

  Manufacturing processes of separators, membranes or diaphragms · CPC title

• H01M50/489

  Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties · CPC title